On Fri, Oct 02, 2009 at 04:05:54PM +0100, Steve Blackmore wrote: > Ehh?
Ehh? > It's sane for any rotary, particularly those that CAN rotate forever. OK, matter of opinion. Let me explain and justify my opinion further down. Simply restating it is silly. > Also as Andy pointed out, you can do an optional short move to zero in > some controllers, invent a code for it if considered essential. OK, I agree a counterproposal might have this scheme. > >Once an axis says "12345.67" you have no > >idea from looking at the number which way it points. You have no > >idea what number to program in either G90 or G91 mode to get it to 90 > >degrees from there without an unwanted 30-ish turn unwind. > > Yes you do? 12435.67 gets it +90 degrees (cw) from 12345.67 or 12255.67 > gets it -90 degrees (ccw) from there. You misunderstand what I meant "to 90 degrees" - let me explain more carefully. My rotary table has marks around it. I want the 90 mark to line up with the pointer. The pointer is currently between some marks. The DRO currently says 12345.67. I want to type a command in MDI to do it. Using the current EMC way, I either type G90 G0 A90 and wait for it to unwind many turns, or I get out my calculator and figure: 12345.67 / 360 = 34.2935 360 * 34 = 12240 12240 + 90 = 12330 OK, so I use G90 G0 A12330 or now I can calculate 12345.67 - 12330 = 15.67 and then use G91 G0 A-15.67 I can now, if I like, reset the DRO to 90 with a G92 A90. If I have not made any mistakes in my calculations this will work. Then, tomorrow when I power up and home the machine, my DRO will still have that offset: it will then read A -12240.00 and at that time I will want to program G92 A0 or G92.1 to fix it. Now instead, with Stuart's proposed system my DRO wouldn't say 12345.67. It would say 105.67 which is also what the pointer is pointing to. I would type G90 G0 A90 if I wanted it to rotate in the positive direction (most of a turn) to get there, or G90 G0 A-90 if I wanted it to rotate the other way to get there. To me this is a VERY clear improvement for a rotary table that's used in indexing mode where the user/programmer doesn't care how many times it has rotated, or possibly even for a forever-rotating head on a 5 axis machine. > I'm objecting strongly to there being no such thing as 360 or bigger, as > Stuart suggested If I have an A axis mounted on my mill and I use it to mill flats to make hex heads on a part, it's exactly true that there is no such thing as 360 or bigger that I care about. If you asked a manual machinist who cranks a rotary table to do this same task, he'd say he uses 0, 60, 120, and so on to do it. He would say funny things about you if you noticed he always cranked his table the same way as he makes these hexes, and you insisted that it was currently set to 12230 degrees! For that kind of use it doesn't matter how many times the rotary has turned. No position information is relevant to the user or programmer except the pointer on the side of the table that points to numbers that could, with this scheme, also be shown on the DRO. I see a use for both systems. I see that you strongly prefer one over the other. I do not understand yet why you object so strongly to the second one being added. Chris ------------------------------------------------------------------------------ Come build with us! The BlackBerry® Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9-12, 2009. Register now! http://p.sf.net/sfu/devconf _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
